The enzyme catalyses three successive methylations of Lys-14 in the large subunits of hexadecameric higher plant ribulose-bisphosphate-carboxylase (EC 4.1.1.39). Only the three methylated form is observed [3]. The enzyme from pea (Pisum sativum) also three-methylates a specific lysine in the chloroplastic isoforms of fructose-bisphosphate aldolase (EC 4.1.2.13) [5].